Thermal analysis on the Li-Mg-B-H systems

Thermal analyses of the mixture of MgH2 and LiBH4 doped with TiCl3, and each element MgH2 or LiBH4 doped with TiCl3 were performed under an inert gas flow and 0.5 MPa H-2-gas conditions. It was indicated that the hydrogen desorption reaction of MgH2 + 2LiBH(4) to MgB2 + 2LiH + 4H(2) phases proceeded at temperature above 400 degrees C under 0.5 MPa hydrogen, whereas, under an inert gas atmosphere, the reaction of the same mixture was transformed into Mg + 2B + 2LiH + 4H(2) phases in a temperature range from 350 to 430 degrees C. Before these reactions, the dehydrogenation of MgH2 and the melting of LiBH4 took place under both hydrogen and the inert gas atmospheres with increasing temperature. In addition, the molten LiBH4 did not decompose into LiH, B and H-2 below 450 degrees C under 1 MPa H-2, while the LiBH4 decomposed even below 450 degrees C under an inert gas atmosphere. From these results, it is deduced that the reaction producing MgB2 is a solid-liquid reaction between solid Mg and liquid LiBH4 above 400 C without decomposition of molten LiBH4 Under a hydrogen atmosphere, while MgH2 dehydrogenate. A characteristic solid-liquid reaction is realized under a hydrogen atmosphere for proceeding of the MgB2 producing reaction in this system. (C) 2007 Elsevier B.V. All rights reserved.